1. Field of the Invention
The present invention relates to an ATM (asynchronous transfer mode) switching apparatus, and more particularly to an ATM switching apparatus with a server function accomplished by a server board.
2. Description of the Related Art
FIG. 1 shows the structure of a conventional multimedia server which is proposed in Japanese Laid Open Patent Application (JP-A-Heisei 7-264196). In the multimedia server, multimedia data bases and a network interface are coupled by an ATM switch apparatus.
As shown in FIG. 1, the conventional multimedia server is composed of a plurality of network interface sections 1 to 4, an ATM switch apparatus 5, a control unit 6, a plurality of data base interface sections 7 to 9, and a plurality of multimedia data bases 10 to 12. Thus, the multimedia server using the ATM switch apparatus 5 is realized. That is, a multimedia data is acquired from the network interface section via the ATM switch apparatus 5.
In the conventional multimedia server, it is presumed that there are few request but a large amount of data is required by each of the requests. Therefore, a large-scale storage is necessary to be provided in advance. For this reason, the conventional multimedia server having such a structure is redundant for a LAN emulation server on an ATM-LAN in which a small amount of data is transmitted for each of a lot of requests.
Also, the method of adding a data base section is not definite. Further, the single control unit is used. The control unit is composed of a processor to determine a complicated request and to reply the request. Therefore, when the number of requests are received from the network interface, the load of the control unit becomes heavy. Thus, there is a possibility that the whole throughput decreases.
In this manner, the conventional multimedia server has the following problems.
The first problem is in that the large-scale storage must be previously incorporated in the multimedia server.
The second problem is in that the method of adding a data base section is indefinite.
The third problem is in that the load of the control unit becomes heavy when the number of requests from the network interface increases. This is because all processes must be performed by the single control unit.
There is a case that a service of an upper layer than an ATM layer is provided as in an LAN (local area network) emulation server and NHRP (Next Hop Resolution Protocol) server. In this case, when a processor as a control unit for controlling the whole apparatus has a server function, the load of the processor becomes heavy. As a result, the processing efficiency decreases. In addition, since a memory area necessary for the server function is used as a memory area necessary for system control, the memory area used for the server is limited.
The present invention is accomplished to solve the above problems. Therefore, an object of the present invention is to provide an ATM switching apparatus in which the load of the control unit can be distributed by installing a server board.
Another object of the present invention is to provide an ATM switching apparatus in which the extension of server functions can be easily performed.
In order to achieve an aspect of the present invention, an asynchronous transfer mode (ATM) switching apparatus provided in a communication network, includes an ATM switch for switching a path for a cell. A control unit controls the ATM switch. A network interface board is installed to interface between the ATM switch and a communication channel for a cell. A server board receives cells from the communication channel through the network interface board and the ATM switch under control of the control unit to provide a service. Also, the server board outputs cells corresponding to the service such that the cells are sent to the communication channel through the network interface board and the ATM switch under control of the control unit.
The server board includes a storage unit for storing a service software, a converting unit and a processor. The converting unit converts the received cells into a reception packet to store the reception packet in the storage unit. Also, the converting unit converts a stored transmission packet to the sent cells to send to the ATM switch. The processor provides the service for the reception packet stored in the storage unit based on the service software to produce the transmission packet, and stores the transmission packet in the storage unit.
The server board can be installed in a physical slot in which the network interface board can be installed.
The ATM switching apparatus may further includes a plurality of the server boards including the server board. The plurality of server boards may provide the same service. In this case, the control unit includes a counter section for counting a number of requests for the service, each of the requests corresponding to the received cells, and controls the path based on the counter section.
Instead, the plurality of server boards may provide different services. In this case, the network interface board informs the service corresponding to the cells to the control unit, and the control unit controls the path based on the information.